Precipitation hardenable nickel and cobalt base superalloys of the gamma-gamma prime type are extensively used in the form of investment castings for gas turbine engine components. Such investment castings can exhibit as-cast surface defects in the form of surface voids. For purposes of illustration, such surface voids can include an as-cast void present on the casting surface when the casting is removed from the shell mold, a void remaining on the casting surface after an inclusion has been removed therefrom, and a crack or crack-like void on the casting surface present when the casting is removed from the investment shell mold. In the past, the presence of such surface voids has been cause for rejection and scrapping of investment castings made of certain unweldable or marginally weldable superalloys, such as for example, MAR-M 247 nickel base superalloy, which cannot be fusion welded without cracking of the base metal heat-affected zone and/or filler material cracking.